Kentucky bluegrass (_Poa pratensis_) is the most widely grown lawn grass in Michigan. It is winter hardy in U.S. Department of Agriculture plant hardiness zones 2 to 7, so it grows well in all parts of the state, which ranges from USDA zone 4 in the Upper Peninsula to zone 6 in the coastal areas of the Lower Peninsula. Kentucky bluegrass also performs well in sandy soils, so it is a good choice for lakeshore regions where sand makes up a significant portion of the soil.
Kentucky Bluegrass Varieties
A study conducted by Michigan State University rated 98 Kentucky bluegrass cultivars in terms of their average turf quality over three consecutive growing seasons. The study ranked the 'Award' cultivar highest, followed by 'North Star,' 'Boutique,' 'Alpine,' 'Unique,' 'Blackstone,' 'Blue Knight,' 'Total Eclipse' and 'Excursion.'
Tall fescue (_Festuca arundinacea_) is a tough grass that is also suitable for Michigan. It is hardy in USDA zone 2 to 7, and it is characterized by a deep root system that helps it to withstand heavy traffic, heat and drought conditions. It doesn't perform as well in cold climates, however, so it is potentially better suited to use in Lower Michigan than in northern regions with harsher winters.
Tall fescue's texture is similar to that of Kentucky bluegrass, but some varieties look quite different and may not blend well if they're used to seed bare or thin spots in bluegrass lawns.
Seed Blends and Mixtures
Seed blends contain more than one cultivar of a single grass species, and seed mixtures contain more than one species. Blends are intended to establish a turf that is more broadly resistant to pest and diseases, since different cultivars may have varying resistance to specific problems. Seed mixtures aim for a combination of species that will perform well in particular growing conditions. Mixtures intended for shady areas, for example, may contain Kentucky bluegrass and fine fescues (_Festuca spp._). Mixtures for sunny areas often include Kentucky bluegrass and perennial ryegrass (_Lolium perenne_). All of these species are hardy in USDA zones 2 to 7.
The best time to plant grass seed in Michigan is in the late summer, typically between the middle of August and the end of September. Grass planted at this time isn't subjected to stress caused by midsummer heat and dry periods, but it has enough time to establish a root system that will help it to survive the winter.
Varieties to Avoid
Some seed mixtures may contain grass species or cultivars that are not suitable for use in lawn turf. 'Kentucky-31' tall fescue, for example, is a coarse, bunching grass that does not work well in lawns. Choose mixtures whose labels include cultivar names and not just species names so that you'll be sure which specific cultivars are included.
Mixtures may also include undesirable grass species that are inadvertently included. These species are usually identified on mixture labels as "crop" seed. Choose mixtures that are labeled as containing less than 1 percent crop seed.